In a storage system, Input/Output or I/O request refers to a communication between a storage device and the host system. The host system will generally make I/O request to a data storage subsystem. The inputs are signals or data received by the storage system, and the outputs are signals or data sent by the storage devices. For efficiency each host can accumulate a batch of I/O requests from users and transmit them to the data storage subsystem. When a storage device is serving multiple hosts the quality of service (QoS) in terms of performance delivered to the host or to different applications running on the same host may vary depending on the overall load on the storage device. There have been multiple implementations to deliver different QoS to different workloads using various scheduling algorithms such as deadline scheduling algorithm.
In the storage system, a number of different devices generally cooperate in order to process a plurality of I/O requests, the result of which is that some devices or components within a system may operate closer to their operating capacity than others, possibly resulting in the creation of processing bottlenecks. In the prior art, service provided by various service components may be distributed among a plurality of tasks by first assigning priority levels to each of the plurality of tasks and then employing a prioritization algorithm, such as time sharing, to determine the distribution of service among the plurality of tasks according to the various priority levels. Where the priority rules for deciding for the processing of the I/O request on components, the data storage system will generally be unable to optimize its performance effectively at run time. Thus, if a data processing application yields a situation in which one of the components is slow in processing, the systems of the prior art will generally continue to process the I/O requests without modification at run time. Accordingly, a processing bottleneck could occur as a consequence of fixing processing priorities prior to beginning program execution.
Other features of the present embodiments will be apparent from the accompanying drawings and from the detailed description that follow.